Method and apparatus for changing frequency for radiosignaling



June 21, 1932. HR T 1,863,564

ING FREQUENCY FOR RADIOSIGNALING METHOD AND APPARATUS FOR CHANG Filed Jan. 14, 1928 2 Sheets-Sheet 1 A (/C/E/Y BET/Elf 5 ITMEIEV June 21, 1932. CHRETIEN 1,863,564 METHOD AND APPARATUS FOR CHANGING FREQUENCY FOR RADIOSIGNALING Filed Jan. 14, 1928 2 Sheets-Sheet 2 INVE/Y TOE L (/C/E/Y NEE T EN Patented June 21, 1932 a UNITED STATES PATENT OFFICE LUGIEN CHRE'IIEN, F PARIS, FRANCE METHOD AND APPARATUS FOR CHANGING FREQUENCY FOR RADIOSIGNALING Application filed January 14, 1928, Serial No. 246,878, and in France January 15, 1927.

The present invention relates to methods current of different and lesser frequency on and apparatus for changing frequency in the outlet side without the adjunction of'a which phenomena analogous to those of the detector or a modulator. The elimination of optical stroboscope are applied to radio sigthe detector is one of the main novel features naling. The invention is particularly adaptof the present invention. Not only is recep- 55 ed for use in radiotelegraphy and radiotion simplified, but amplification and change telephony and permits considerable simpliof frequency are effected by the same electron fication of the apparatus now required and tube in a single operation.

a notable increase in the sensitiveness of re- The invention will now be described in deception. tail with reference to the accompanying draw- 60 The present method is carried out by peings in which: riodically varying at an appropriate fre- Fig. 1 is a diagram ofone constructive emquency the damping effect of the circuit bodimcnt 0f the invention, traversed by the current whose frequency is F 1g. 2 illustrates the functioning of the de to be changed by means of a periodic varia- Vi ShOWn in Fig. l, 65 tion of an impedance placed in parallel or ig- 3 r presents a'second form of the inin series with the circuit in question. volition,

T obtain wid ariations in th im d- Fig. 4 shows a complete receiving set conance, i. e. values passing alternately fro structed in accordance with the invention.

a value of zero to value of infinity, it is only l g 0 F 1 g- 1, there is shown an elec- 70 necessary to introduce an ordinary periodic tIOII tube 1 II mIIg a filament 2, a grid 3 niake-and-break device, the making and the and a p at 4; Fllamentg is heated by a breaking action of the latter functioning to t y Whil la e 4 is brought to the produce the limiting values desired. In an deslred p n l l fy m ans of a battery 6.

bl f thi ki d assuming f t b th The current whose requency is to be changed 75 frequency of the current to be transformed fl through 9111111113 7, 8 whereln it may be and f the frequency of the make-and-break y lnseltlng 8 111 osclllatlng action, the circuit carrying current at frecllcult of an antenna y p g the quency f will simultaneously carry a pul- H161 to l 9 ,agam y means sating current of an amplitude varying with 9 1 all-"Cult 8 lllselted 1Ilt0 he grld 0 the difference of frequency f f f 3 circuit of tube 1 so that the impedance of cording as f is greater or less than F. These h? Space between filament 2 and t gl'ld pulsations may be selected in acoupled cir Parallel r l io to t rmlnals of cuit and frequency 7 will thus have been c1TCult7,8- Thls lmpedance W P rtransformed to a frequency f f without y 9 Value substantlany Zero a recourse to interference, detecting or modu- Value 9 mfimty under F effect 9 m y lating phenomena potentials applied to grid 3 by a circuit 9, 10

In actual practice the make-and-break ef- Carry a Osclnatlng current P Q y foot is conveniently obtained by the use of means of Inductance 10 up d o n inducan electron tube arranged as an amplifier. m 11 HrIB Gd t0 the plate circuit. In- The required periodic interruptions are productflnfle 11 1S 3150 Connected to EL lrcult 12, duced at appropriat fr qu y b id l l3 destined to carry the current of changed varying thev grid potential, the variations requency- A p p 1ng 13, 14 may be arbeing produced either by an auxiliary gen. ranged in inductive relation to 12, 13 and the eration circuit connected tothe tube or by current induced may be led off to an amplifier a second electron tube. or to any other form of apparatus desired.

The circuits feeding current to the assem- In order to avoid undesirable reactions bebled device are arranged so that a current of tween the auxiliary generating circuit 9, 1O given frequency applied to the entering side and circuit 7, 8, the connection between these 50 of the apparatus gives rise to an amplified two circuits-which is necessary in order to close the grid circuit-is best effected at the median electrical point 15 of inductance 10. Since the median geometric point of the inductance does not always coincide with the median electric point, some difliculty is encountered, in actual practice, in locating the latter of these two points. To obviate this difficulty, circuit 9, 10 may be made one member. of a WVheatstone bridge. The median electric point of the inductance may then be found with ease. The may be set up in the following way: The two sections of inductance 10- constitute two branches, two condensers 16, 17 constitute the other two' branches and condenser 9 the diagonal of the bridge. By connecting the common point 18 of condensers 16,17 to point 15, and regulating one or both of the condensers, point 15, be it the geometric median or some other point on inductance 10, may be made to constitute the median electric point. Inductance 10 may thus be made-up of two parts 10 and 10 and the conductorconnecting points be connected to circuit 7 8. It is to be understood, of course, that the VYheatstone assembly'may be inserted at any point in the grid circuit.

This grid circuit is devoid of any detecting elements and is simply connected to the negative pole of heating battery 5 so that tube 1 functions as an amplifier. V

The manner in which the above described apparatus functions is as follows:

. Circuit 7 8 carries a current of frequency 1 the same time a current of frequency f is produced in circuit 9, 10. Under the effect of this current, the potential of grid 3 will vary at frequency Tube 1 can only amplify between well-defined values of the grid potential. When grid 3 becomes positive under the .efiects of the current of frequency the damping caused by the impedance of the space between the filament and the grid, when the positive charges exceed a certain value, will cause a displacement of'the operating point toward the upper part of the characteristic provided the amplitude of the current of frequency f is sufliciently great.

The upper curvature of the characteristic'is thus reached and current of frequency f prevented from following. \lVhen, contrariwise, grid 3 is negative, the impedance of the space between the filament and the grid is practically infinite and the damping effect of c-ircuit 7, 8 is entirely eliminated. Current of frequency f can then pass freely. The end effect is then to superpose on the current of frequency f flowing in the circuit of plate 4, aseries of impulses proportional at each instant to the potential produced by the incident current of frequency 7. These impulses combine to yield a current of frequency f -f Fig. 2 shows graphically how the \Vh'eatstone bridge 15 and 18 of the bridge may then whose frequency is to be changed. At

foregoing phenomena take place. Curve A represents the current of frequency f whose frequency is to be changed, curve B the local current of frequency f and curve C the current of frequency 7 -7. The quantity of electricity transmitted to the grid circuit during a time interval 2f 2 has a mean value equal to the difference of the values of the cross-hatched portions such as 0, w, p and y, etc. The mean current in the plate circuit is proportional to this quantity of electricity. There is a cutting up, so to speak, of the oscillations of frequency f at the rate of f times per second, and, because of the difference between f and 7, that portion of current 7 which is transmitted gradually moves out of phase as in the case of stroboscopic' phenomena. The total exploration of a complete period is accomplished at the rate of f -j' times per second. The phenomenon is somewhat analogous to that applied in the Hospitalier ondograph for reconstituting a low frequency wave at extremely low frequency.

Condensers 16 and 17, which are in parallel with condenser 9 should be of small capacity so as not to increase the residual capacity of the latter. A convenient arrangement in practice is to combine the two condensers into a single structureconsisting of a pair of fixed armatures19 and 20 provided with a common movable armature 21 as shown in Fig. 3. Under certain conditions it may be preferable to apply to the circuit of grid 3 only a fraction of the voltage of circuit 7, 8. In such a case an adjustable slide 22 is provided which permits the insertion of 'all, or a part of inductance 7 in the grid circuit.

A. frequency changer of the type above decribed lends itself advantageously to applications involvingthe reception of radio signals. When so applied, the apparatus is designed so that thetransformed current is of inaudible frequency. It will then be necessary to detect thiscurrent if perceptible effee-ts are to be produced in a telephone re: ceiver.

It is, of course, to be understood that the frequency changer may be preceded or followed or both preceded and followed by amplifying devices.

Fig. 4 shows a receivingassembly fitted with the frequency changer forming the subject matter of the presentinvention.

Electron tube 23 is a high frequency amplifier preceding frequency changing tube-1, the latter being followed by two amplifying tubes 24, 25 feeding a detectingtube 26 which delivers current to a low frequency amplifying tube 27.

Signalsare arrested by some such device as loop 28 which is tuned by variable condenser 29 and are then transmitted to grid 30 of tube 23. Preferably the potential applied to grid 30 is regulated by a potentiometer 31 supplied with current from heating battery 32. A condenser 33 is connected in parallel between the negative pole of battery 32 and the slide of potentiometer 31 so as to permit easy passage of high frequency currents.

Amplifying tube 23 is connected to frequency changing tube 1 in a special way, to wit: by means of a triple wound transformer having a primary winding 34 inserted in the circuit of plate 35, a secondary winding 36 arranged to be tuned by variable condenser 37, and a third winding 38 coupled with secondary 36 and connected into the grid circuit of frequency changing tube 1. The third Winding functions, here, as the equivalent of circuit 7, 8 shown in Figs. 1 and 3. This special manner of connecting amplifying tube 23 to tube 1 has the advantage of permitting a very fine selectivity largely because it avoids the damping action exerted by tube 1 on circuit 36, 37. In certain cases, it may be desirable to define the potential of this circuit by connecting movable armature 37 to a point of constant potential such as the negative pole of heating battery 32, the latter being then connected to the earth. The capacity due to the body of the operator is thus eliminated. In order to avoid the effect of incoming disturbing oscillations a neutralizing condenser 39, shown in dotted lines, may be inserted between grid 30 of tube 23 and grid 3 of tube 1.

The oscillations amplified by tube 23 are transformed as to frequency by tube 1 as already described. The current of changed frequency will appear in circuit 12, 13 and, by regulating the various circuits on the feed side of tube 1, may be adjusted to an inaudible frequency. The current flowing in 12, 13 is then transmitted by coupling 13, 14 fitted with tuning condenser 40 to amplifying tubes 24, 25. The latter are coupled by means of transformers 41, 42 having secondary windings tuned to the frequency of the transformed current by variable condensers 43, 44. The several transformer-condenser groups such as 41, 43 may be inclosed in a metallic box 45 functioning as a Faraday cage. In addition, the various tuned secondary windings may be connected through a common point 46 to box 45, so as to avoid the direct disturbing effects on the various circuits. If desired, a potentiometer 47 may be employed for adjusting the potential of the grids of amplifying tubes 24 and 25. In this case, a condenser 48 is inserted between the negative pole of heating battery 32 and the slide of the potentiometer.

The current thus transformed and amplified may then be detected by tube 26 and transmitted through transformer 49 to a low frequency amplifier 27 having a telephone or a loud speaker 50 connected to its plate circuit. The plates of the various electron tubes are raised to proper potential by a battery 51. In order that tube 1 may function properly, it is preferable to raise plate 4 to a desired potential by manipulating appropriate varying means 52 associated with battery 51.

It is to be understood that the invention is not to be taken as limited to the particular devices described. Thus, the number of amplifying tubes preceding or following the frequency changer may be varied at will; any number of stages of low-frequency amplification may be introduced; and the manner of coupling the amplifying tubes may be varied.

Having now described my invention, What I claim as new and desire to secure by Letters Patent, is

1. A device for changing frequency having a three-element electron tube and inductively coupled grid and plate circuits, comprising a first oscillating circuit furnishing a local frequency, a second oscillating circuit carrying the frequency to be transformed, said first and second circuits being introduced both into the said grid circuit, a third oscillating circuit introduced into the plate circuit and carrying the transformed frequency, and a pair of variable condensers each having one of their plates connected to the terminals of said first oscillating circuit, the other plates being connected to the middle point of the inductance of said first oscillating circuit forming an equipotential connection to which is connected the second oscillating circuit.

2. A device for changing frequency having a three-element electron tube and inductively coupled grid and plate circuits, comprising a first a local frequency, a second oscillating circuit carrying the frequency to be transformed, said first and second circuits being inserted in the grid circuit, a third oscillating circuit introduced into the plate circuit and carrying the transformed frequency, a pair of variable condensers having common movable plate. an equipotential connection between the middle point of the inductance of said first oscillating circuit and said common movable plate,

the other plates of said variable condensers being connected respectively to theterminals of the condenser of the first oscillating circuit.

3. A device for changing frequency having a three-element vacuum tube and inductively coupled grid and anode circuits, comprising a first oscillating circuit furnishing a local frequency, a second oscillating circuit carrying the frequency to be transformed, said first and second circuits being introduced into said grid circuit, a third oscillating circuit introduced into said anode circuit and carrying the current with transformed frequency, a pair of variable condensers having a common movable plate, connections joinin the fixed plates of said condensers to ioo oscillating circuit furnishing g the first oscillating circuit, an equ'ipoten'tial connection joining said common movable plate to the middle point of the inductance of said first oscillating circuit and a connection join ing said equipotential connection to a variable point of the inductance of the second oscillating circuit.

4. A device for changing frequenc having a three-element vacuum tubeand in uctively coupled grid and anode circuits, comprising a first oscillating circuit furnishing a local current, a first coil carrying the current to be transformed, both being introduced into said grid circuit, a second oscillating circuit inductively coupled with said first coil, a second coil receiving the current to be transformed and inductively coupled with said second circuit, a third oscillating circuit introduced into said anode circuit and carrying the current whose frequency has been transformed, a pair of variable condensers having a common movable plate, connections joining the fixed plates of said condensers with the first oscillating circuit, an equipotential connection joining said common movable plate to the middle point of the inductance of said first oscillating circuit, and a connection joining the first coil to said equipotential connection.

5. A device for changing frequency for radio-reception comprising an electron tube amplifying the incident oscillations to be transformed, a three-element vacuum tube for changing the frequency of said incident oscillations having the grid and anode circuit coupled inductively, a first oscillating circuit introduced into said grid circuit, a pair of variable condensers havinga common movable plate, an equipotential connection connecting said movable plate to themiddle point of the inductance of said oscillating circuit, connections joining the fixed plates of said condensers to said oscillating circuit, a first coil introduced into the anode circuit of the amplifying tube, a second oscillating circuit inductivelycoupled-to said first coil, a second coil inductively coupled to said second oscillating circuit and connected between the filament of the frequency transforming tube and said equipotential connection, and a neutralizing condenser placed between said equipotential connection and the control electrode of the amplifying tube. V

LUCIEN CHRETIEN. 

